Holographic scanner for reconstructing a scanning light spot insensitive to a mechanical wobble

Abstract

A holographic spinner reconstructs a light spot to rapidly scan a narrow line on a suitable "write" surface to generate an image. The geometry of the holographic spinner with respect to the holographic reconstruction light beam is such that the position of the regenerated light spot is insensitive to mechanical wobble which might be present in the spinner mechanism.

What is claimed is: 
     
       1. A holographic raster scanning system including: a source of coherent light,   a hologram disposed in the path of a reconstruction light wavefront and a principal light ray thereof from said source and mounted for rotation to effect the transverse movement of said hologram relative to said wavefront and said principal light ray,   said hologram effective to transmit said wavefront and said principal light ray, incident thereon at an angle of incidence φ i , and to diffract said principal ray at a first order diffraction angle φ d , to reconstruct an image wavefront forming a spot of light for scanning when said hologram is rotated,   said hologram being disposed relative to said principal light ray such that said angles of incidence and diffraction are substantially equal,   said wavefront and said hologram being further disposed so that said wavefront is substantially radially symmetrical relative to the axis of rotation of said hologram, said symmetry being achieved by directing said wavefront so that its apparent, or real, origin is a point on said hologram axis of rotation   whereby the reconstructed image wavefront propagating from said hologram and the projected spot of light are substantially invariant in the presence of varying degrees of tilt of said hologram relative to said principal light ray when said hologram is rotating.